Filter for a pneumatic tire

ABSTRACT

A pneumatic tire assembly includes a tire having a pneumatic cavity and a filter disposed between the pneumatic cavity and atmosphere. The filter is constructed of a hydrophobic material for avoiding all liquid adhesion. First and second sidewalls extend respectively from first and second tire bead regions to a tire tread region. The first sidewall has at least one bending region operatively bending when radially within a rolling tire footprint. A sidewall groove is defined by groove walls positioned within the bending region of the first tire sidewall. The sidewall groove deforms segment by segment between a non-deformed state and a deformed, constricted state in response to bending of the bending region of the first sidewall while radially within the rolling tire footprint.

FIELD OF THE INVENTION

The present invention relates generally to filtering air for a pneumatic tire and, more specifically, to filtering air into a pumping assembly for a pneumatic tire.

BACKGROUND OF THE INVENTION

Normal air diffusion reduces tire pressure over time. The natural state of tires is under inflated. Accordingly, drivers must repeatedly act to maintain tire pressures or they will see reduced fuel economy, tire life and reduced vehicle braking and handling performance. Tire Pressure Monitoring Systems have been proposed to warn drivers when tire pressure is significantly low. Such systems, however, remain dependant upon the driver taking remedial action when warned to re-inflate a tire to recommended pressure. It is a desirable, therefore, to incorporate an air maintenance feature within a tire that will maintain air pressure within the tire in order to compensate for any reduction in tire pressure over time without the need for driver intervention.

SUMMARY OF THE INVENTION

A pneumatic tire assembly in accordance with the present invention includes a tire having a pneumatic cavity and a filter disposed between the pneumatic cavity and atmosphere. The filter is constructed of a hydrophobic material for avoiding all liquid adhesion. First and second sidewalls extend respectively from first and second tire bead regions to a tire tread region. The first sidewall has at least one bending region operatively bending when radially within a rolling tire footprint. A sidewall groove is defined by groove walls positioned within the bending region of the first tire sidewall. The sidewall groove deforms segment by segment between a non-deformed state and a deformed, constricted state in response to bending of the bending region of the first sidewall while radially within the rolling tire footprint. An air passageway is defined by the sidewall groove and deforms segment by segment between an expanded condition and an at least partially collapsed condition in response to respective segment by segment deformation of the sidewall groove when radially within the rolling tire footprint.

According to another aspect of the pneumatic tire assembly, the filter includes a filter support housing defining a membrane seat for receiving an air membrane for air filtration.

According to still another aspect of the pneumatic tire assembly, the filter support housing includes an air outlet for supplying air to the air passageway.

According to yet another aspect of the pneumatic tire assembly, the air membrane comprises polytetrafluoroethylene.

According to still another aspect of the pneumatic tire assembly, the filter includes a hydrophilic material for capturing liquid to clean a membrane surface of the air membrane.

According to yet another aspect of the pneumatic tire assembly, the air membrane comprises multiple membranes stacked on each other in order to utilize differing porosities of different membrane materials.

According to still another aspect of the pneumatic tire assembly, the filter includes an O-ring for sealing the filter support housing to the tire.

According to yet another aspect of the pneumatic tire assembly, the filter includes a filter lock member for securing the air membrane to the filter support housing.

According to still another aspect of the pneumatic tire assembly, the filter lock member includes air inlets for supplying ambient air to the air passageway.

According to yet another aspect of the pneumatic tire assembly, the air inlets are coated with the hydrophobic material to facilitate liquid flow through the filter.

A method maintains air pressure in a pneumatic tire cavity. The method includes the steps of placing a filter between the pneumatic cavity and atmosphere, the filter being constructed of a hydrophobic material for avoiding liquid adhesion and deforming an air passageway segment by segment between an expanded condition and an at least partially collapsed condition in response to respective segment by segment deformation of a sidewall groove when radially within a rolling tire footprint.

According to another aspect of the method, a further step includes securing an air membrane to a membrane seat of a filter support housing.

According to still another aspect of the method, a further step includes supplying air to the air passageway.

According to yet another aspect of the method, the air membrane includes polytetrafluoroethylene.

According to still another aspect of the method, a further step includes capturing liquid by a hydrophilic material.

According to yet another aspect of the method, a further step includes stacking multiple membranes in order to utilize differing porosities of different membrane materials for air filtration.

According to still another aspect of the method, a further step includes sealing the filter support housing to the tire with an O-ring.

According to yet another aspect of the method, a further step includes securing the air membrane to the filter support housing by a filter lock member.

According to still another aspect of the method, a further step includes supplying ambient air to the air passageway by an air inlet of the filter lock member.

According to yet another aspect of the method, a further step includes coating the air inlet with the hydrophobic material to facilitate liquid flow through the filter.

DEFINITIONS

“Aspect ratio” of the tire means the ratio of its section height (SH) to its section width (SW) multiplied by 100 percent for expression as a percentage.

“Asymmetric tread” means a tread that has a tread pattern not symmetrical about the center plane or equatorial plane EP of the tire.

“Axial” and “axially” means lines or directions that are parallel to the axis of rotation of the tire.

“Chafer” is a narrow strip of material placed around the outside of a tire bead to protect the cord plies from wearing and cutting against the rim and distribute the flexing above the rim.

“Circumferential” means lines or directions extending along the perimeter of the surface of the annular tread perpendicular to the axial direction.

“Equatorial Centerplane (CP)” means the plane perpendicular to the tire's axis of rotation and passing through the center of the tread.

“Footprint” means the contact patch or area of contact of the tire tread with a flat surface at zero speed and under normal load and pressure.

“Groove” means an elongated void area in a tire dimensioned and configured in section for receipt of an air tube therein.

“Hydrophilic material” means a material that tends to interact with, be dissolved by, and/or is attracted to water or liquid. Hydrophilic substances (e.g., salts, sugars, etc.) may seem to attract water out of the air.

“Hydrophobic material” means a material that seemingly repels water or liquid. Strictly speaking, there is no repulsive force involved; it is an absence of attraction. Examples of hydrophobic molecules include alkanes, oils, fats, and greasy substances, in general.

“Inboard side” means the side of the tire nearest the vehicle when the tire is mounted on a wheel and the wheel is mounted on the vehicle.

“Lateral” means an axial direction.

“Lateral edges” means a line tangent to the axially outermost tread contact patch or footprint as measured under normal load and tire inflation, the lines being parallel to the equatorial centerplane.

“Net contact area” means the total area of ground contacting tread elements between the lateral edges around the entire circumference of the tread divided by the gross area of the entire tread between the lateral edges.

“Non-directional tread” means a tread that has no preferred direction of forward travel and is not required to be positioned on a vehicle in a specific wheel position or positions to ensure that the tread pattern is aligned with the preferred direction of travel. Conversely, a directional tread pattern has a preferred direction of travel requiring specific wheel positioning.

“Outboard side” means the side of the tire farthest away from the vehicle when the tire is mounted on a wheel and the wheel is mounted on the vehicle.

“Peristaltic” means operating by means of wave-like contractions that propel contained matter, such as air, along tubular pathways.

“Radial” and “radially” means directions radially toward or away from the axis of rotation of the tire.

“Rib” means a circumferentially extending strip of rubber on the tread which is defined by at least one circumferential groove and either a second such groove or a lateral edge, the strip being laterally undivided by full-depth grooves.

“Sipe” means small slots molded into the tread elements of the tire that subdivide the tread surface and improve traction, sipes are generally narrow in width and close in the tires footprint as opposed to grooves that remain open in the tire's footprint.

“Tread element” or “traction element” means a rib or a block element defined by a shape with adjacent grooves.

“Tread Arc Width” means the arc length of the tread as measured between the lateral edges of the tread.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be described by way of example and with reference to the accompanying drawings, in which:

FIG. 1; Schematic view of an example filter.

FIG. 2; Side view of the example tire/tube assembly.

FIG. 3A-3C; Details of an example outlet connector.

FIG. 4A-4E; Details of an example inlet (filter) connector.

FIG. 5A; Side view of an example tire rotating with air movement (84) to cavity.

FIG. 5B; Side view of the example tire rotating with air flushing out filter.

FIG. 6A; Section view taken from FIG. 5A.

FIG. 6B; Enlarged detail of tube area taken from FIG. 6A, sidewall in non-compressed state.

FIG. 7A; Section view taken from FIG. 5A.

FIG. 7B; Enlarged detail of tube area taken from FIG. 7A, sidewall in compressed state.

FIG. 8A; Enlarged detail of an example tube & groove detail taken from FIG. 2.

FIG. 8B; Detail showing an example tube compressed and being inserted into the groove.

FIG. 8C; Detail showing an example tube fully inserted into the groove at a ribbed area of the groove.

FIG. 8D; Exploded fragmented view of tube being inserted into a ribbed groove.

FIG. 9; Enlarged detail taken from FIG. 2 showing an example rib profile area located on both sides of the outlet to a cavity connector.

FIG. 10A; Enlarged detail of the groove with the example rib profile.

FIG. 10B; Enlarged detail of tube pressed into the example rib profile.

FIG. 11; Enlarged detail taken from FIG. 2 showing another example rib profile area located on both sides of the outlet to a cavity connector.

FIG. 12A; Enlarged detail of the groove with the other example rib profile.

FIG. 12B; Enlarged detail of the tube pressed into the other example rib profile.

FIG. 13A; Enlarged view of another example tube & groove detail.

FIG. 13B; Detail showing tube from FIG. 13A being compressed and inserted into the groove.

FIG. 13C; Detail showing the tube from FIG. 13A fully inserted into the groove.

FIG. 14A; Enlarged view of a third example tube & groove detail.

FIG. 14B; Detail showing tube from FIG. 14A being compressed and inserted into the groove.

FIG. 14C; Detail showing the tube from FIG. 14A fully inserted into the groove.

FIG. 15A; Enlarged view of a fourth example tube & groove detail.

FIG. 15B; Detail showing tube from FIG. 15A being compressed and inserted into the groove.

FIG. 15C; Detail showing the tube from FIG. 15A fully inserted into the groove.

FIG. 16; Isometric exploded view of an example tire and tube assembly.

FIGS. 17A & 17B; Schematic view of an example filter in accordance with the present invention.

FIGS. 18A & 18B; Schematic exploded view of the filter of FIGS. 17A & 17B.

DETAILED DESCRIPTION OF EXAMPLES OF THE PRESENT INVENTION

Referring to FIGS. 16, 2, and 6A, an example tire assembly 10 may include a tire 12, a peristaltic pump assembly 14, and a tire rim 16. The tire may mount in conventional fashion to a pair of rim mounting surfaces 18, 20 adjacent outer rim flanges 22, 24. The rim flanges 22, 24 each have a radially outward facing flange end 26. A rim body 28 may support the tire assembly 10 as shown. The tire 12 may be of conventional construction, having a pair of sidewalls 30, 32 extending from opposite bead areas 34, 36 to a crown or tire tread region 38. The tire 12 and rim 16 may enclose a tire cavity 40.

As seen from FIGS. 2 and 3A, 3B, 3C, 6B and 8A, the example peristaltic pump assembly 14 may include an annular air tube 42 that encloses an annular passageway 43. The tube 42 may be formed of a resilient, flexible material such as plastic or rubber compounds that are capable of withstanding repeated deformation cycles of a flattened condition subject to external force and, upon removal of such force, returned to an original condition generally circular in cross-section. The tube 42 may have a diameter sufficient to operatively pass a volume of air for purposes described herein and allowing a positioning of the tube in an operable location within the tire assembly 10 as will be described below. In the example configuration shown, the tube 42 may be an elongate, generally elliptical shape in cross-section, having opposite tube sidewalls 44, 46 extending from a flat (closed) trailing tube end 48 to a radiussed (open) leading tube end 50. The tube 42 may have a longitudinal outwardly projecting pair of locking detent ribs 52 of generally semi-circular cross-section and each rib extending along outward surfaces of the sidewalls 44, 46, respectively.

As referenced in FIG. 8A, the tube 42 may have a length L1 within a range of 3.65 mm to 3.80 mm; a width of D1 within a range of 2.2 mm to 3.8 mm; a trailing end width of D3 within a range of 0.8 mm to 1.0 mm. The protruding detent ribs 52, 54 may each have a radius of curvature R2 within a range of 0.2 mm to 0.5 mm and each rib may be located at a position distance L3 within a range of 1.8 mm to 2.0 mm of the trailing tube end 48. The leading end 50 of the tube 42 may have a radius R1 within a range of 1.1 mm to 1.9 mm. The air passageway 43 within the tube 42 may likewise be generally elliptical with a length L2 within a range of 2.2 mm to 2.3 mm; and a width D2 within a range of 0.5 mm to 0.9 mm.

The tube 42 may be profiled and geometrically configured for insertion into a groove 56. The groove 56 may have an elongate, generally elliptical configuration with a length L1 within a range of 3.65 mm to 3.80 mm complementary to the elliptical shape of the tube 42. The groove 56 may include a restricted narrower entryway 58 having a nominal cross-sectional width D3 within a range of 0.8 mm to 1.0 mm. A pair of groove-rib receiving axial detent channels 60, 62 of semi-circular configuration may be formed within opposite sides of the groove 56 for corresponding receipt of the tube locking ribs 52, 54, respectively. The channels 60, 62 may be spaced approximately a distance L3 within a range of 1.8 mm to 2.0 mm of the groove entryway 58. Detent channels 60, 62 may each have a radius of curvature R2 within a range of 0.2 mm to 0.5 mm. An inward detent groove portion 64 may be formed with a radius of curvature R1 within a range of 1.1 mm to 1.9 mm and a cross-sectional nominal width D1 within a range of 2.2 mm to 3.8 mm.

As best seen from FIGS. 8D, 9, 10A and 10B, the tire 12 may further form one or more compression ribs 66 extending the circumference of, and projecting into, the groove 56. The ribs 66 may form a pattern of ribs of prescribed pitch, frequency, and location, as described below. For the purpose of explanation, seven compression ribs may be referred to generally by numeral 66 in the first rib profile pattern shown, and specifically by the rib designations D0 through D6. The ribs D0 through D6 may be formed in a sequence and pitch pattern in order to optimize the pumping of air through the tube passageway 43. The ribs 66 may each have a unique and predetermined height and placement within the pattern and, as shown in FIG. 8D, project outward into the groove 56 at a radius R3 (FIG. 8A) within a range of 0.95 mm to 1.60 mm.

With reference to FIGS. 16, 2, 3A through 3C, and 4A through E, the peristaltic pump assembly 14 may further include an inlet device 68 and an outlet device 70 spaced apart approximately 180 degrees at respective locations along the circumferential air tube 42. The example outlet device 70 has a T-shaped configuration in which conduits 72, 74 direct air to, and from, the tire cavity 40. An outlet device housing 76 contains conduit arms 78, 80 that integrally extend from respective conduits 72, 74. Each of the conduit arms 78, 80 have external coupling ribs 82, 84 for retaining the conduits within disconnected ends of the air tube 42 in the assembled condition. The housing 76 is formed having an external geometry that complements the groove 56 and includes a flat end 86, a radiused generally oblong body 88, and outwardly projecting longitudinal detent ribs 90. The housing 76 may thus be capable of close receipt into the groove 56 at its intended location with the ribs 90 registering within the groove 56 as represented in FIG. 8A.

The inlet device 68, as seen in FIGS. 12, 4A through 4E, may include an elongate outward sleeve body 94 joining an elongate inward sleeve body 96 at a narrow sleeve neck 98. The outward sleeve body is generally triangular in section. The inward sleeve body 96 has an oblong external geometry complementary to the groove 56 and includes a pair of detent ribs 100 extending longitudinally along the inward sleeve body. An elongate air entry tube 101 is positioned within the inward sleeve body 96 and includes opposite tube ends 102 and a pattern of entry apertures 104 extending into a central tube passageway. External ribs 106, 108 secure the tube ends 102 in the air tube 42 opposite the outlet device 70.

As shown in FIGS. 6A, 6B, 7A, 7B, 8A through D, the pump assembly 14 may comprise the air tube 42 and inlet and outlet devices 68, 70 affixed in-line to the air tube at respective locations 180 degrees apart when inserted into the groove 56. The groove 56 may be located at a lower sidewall region of the tire 12 that, when the tire is mounted to the rim 16, positions the air tube 42 above the rim flange ends 26. FIG. 8B shows the air tube 42 diametrically squeezed and collapsed to accommodate insertion into the groove 56. Upon full insertion, as shown in FIG. 8C, the ribs 52, 54 may register within the groove channels 60, 62 and the flat outer end 48 of the tube 42 may be generally coplanar with the outer surface of the sidewall of the tire. Once fully inserted, the air passageway 43 of the tube 42 may elastically restore itself into an open condition to allow the flow of air along the tube during operation of the pump.

Referring to FIGS. 16, 2, 5A, 5B, 6A, 6B, 7A, 7B, 8A through 8D, the inlet device 68 and the outlet device 70 may be positioned within the circumference of the circular air tube 42 generally 180 degrees apart. The tire 12 with the tube 42 positioned within groove 56 rotates in a direction of rotation 110, causing a footprint 120 to be formed against the ground surface 118. A compressive force 124 is directed into the tire 12 from the footprint 120 and acts to flatten a segment of the air tube passageway 43 opposite the footprint 120, as shown at numeral 122. Flattening of a segment of the passageway 43 forces air from the segment along the tube passageway 43 in the direction shown by arrow 116, toward the outlet device 70.

As the tire 12 continues to rotate in the direction 110 along the ground surface 118, the tube 42 may be sequentially flattened or squeezed opposite the tire footprint, segment by segment, in a direction opposite to the direction 110. A sequential flattening of the tube passageway 43, segment by segment, may cause evacuated air from the flattened segments to be pumped in the direction 116 within tube passageway 43 toward the outlet device 70. Air may flow through the outlet device 70 and to the tire cavity 40, as shown at 130. At 130, air exiting the outlet device 70 may be routed to the tire cavity 40 and serve to re-inflate the tire 12 to a desired pressure level. A valve system to regulate the flow of air to the cavity 40, when the air pressure within the cavity falls to a prescribed level, is shown and described in pending U.S. patent applicant Ser. No. 12/775,552, filed May 7, 2010, and incorporated herein by reference.

With the tire 12 rotating in direction 110, flattened tube segments may be sequentially refilled by air flowing into the inlet device 68 in the direction 114, as shown by FIG. 5A. The inflow of air into the inlet device 68, and then into the tube passageway 43, may continue until the outlet device 70, rotating in a counterclockwise direction 110, passes the tire footprint 120. FIG. 5B shows the orientation of the peristaltic pump assembly 14 in such a position. The tube 42 may continue to be sequentially flattened, segment by segment, opposite the tire footprint 120 by a compressive force 124. Air may be pumped in the clockwise direction 116 to the inlet device 68 and evacuated or exhausted external to the tire 12. Passage of exhaust air, as shown at 128, from the inlet device 68 may occur through a filter sleeve 92 exemplarily formed of a cellular or porous material or composite. Flow of air through the filter sleeve 92 and into the tube 101 may thus cleanse debris or particulates. In the exhaust or reverse flow of air direction 128, the filter sleeve 92 may be cleansed of trapped accumulated debris or particles within the porous medium. With the evacuation of pumped air out of the inlet device 68, the outlet device 70 may be in a closed position preventing air flow to the tire cavity 40. When the tire 12 rotates further in counterclockwise direction 110 until the inlet device 70 passes the tire footprint 120 (as shown in FIG. 5A), the airflow may resume to the outlet device and cause the pumped air to flow out and into the tire cavity 40. Air pressure within the tire cavity 40 may thus be maintained at a desired level.

FIG. 5B illustrates that the tube 42 is flattened, segment by segment, as the tire 12 rotates in direction 110. A flattened segment 134 moves counterclockwise as it is rotated away from the tire footprint 120 while an adjacent segment 132 moves opposite the tire footprint and is flattened. Accordingly, the progression of squeezed or flattened or closed tube segments may be move air toward the outlet device 70 (FIG. 5A) or the inlet device 68 (FIG. 5B) depending on the rotational position of the tire 12 relative to such devices. As each segment is moved by tire rotation away from the footprint 120, the compression forces within the tire 12 from the footprint region may be eliminated and the segment may resiliently reconfigure into an unflattened or open condition as the segment refills with air from the passageway 43. FIGS. 7A and 7B show a segment of the tube 42 in the flattened condition while FIGS. 6A and 6B show the segment in an expanded, unflat or open configuration prior to, and after, moving away from a location opposite the tire footprint 120. In the original non-flattened configuration, segments of the tube 42 may resume the exemplary oblong generally elliptical shape.

The above-described cycle may repeat for each tire revolution, with half of each rotation resulting in pumped air moving to the tire cavity 40 and half of each rotation resulting in pumped air moving back out the filter sleeve 92 of the inlet device 68 for self-cleaning the filter. It may be appreciated that while the direction of rotation 110 of the tire 12 is as shown in FIGS. 5A and 5B is counterclockwise, the subject tire assembly 10 and its peristaltic pump assembly 14 may function in a like manner in a reverse (clockwise) direction of rotation as well. The peristaltic pump assembly 14 may accordingly be bi-directional and equally functional with the tire 12 and vehicle moving in a forward or reverse direction of rotation and forward or reverse direction of the vehicle.

The air tube/pump assembly 14 may be as shown in FIGS. 5A, 5B, 6A, 6B, 7A and 7B. The tube 42 may be located within the groove 56 in a lower region of the sidewall 30 of the tire 12. The passageway 43 of the tube 42 may close by compression strain bending of the sidewall groove 56 within a rolling tire footprint 120, as explained above. The location of the tube 42 in the sidewall 30 may provide freedom of placement thereby avoiding contact between the tube 42 and the rim 16. Higher placement of the tube 42 in the sidewall groove 56 may use high deformation characteristics of this region of the sidewall as it passes through the tire footprint 120 to close the tube 42.

The configuration and operation of the grooved sidewalls, and in particular the variable pressure pump compression of the tube 42 by operation of ridges or compression ribs 66 within the groove 56 is shown in FIGS. 8A-8D, 9, 10A and 10B. The ridges or ribs are indicated by numeral 66 and individually as D0 through D6. The groove 56 may be uniform width circumferentially along the side of the tire 12 with the molded ridges D0 through D6 formed to project into the groove 56 in a preselected sequence, pattern, or array. The ridges D0 through D6 may retain the tube 42 in a predetermined orientation within the groove 56 and also may apply a variable sequential constriction force to the tube.

The uniformly dimensioned pump tube 42 may be positioned within the groove 56 as explained above—a procedure initiated by mechanically spreading the entryway D3 of the groove 56 apart. The tube 42 may then be inserted into the enlarged opening of the groove 56. The opening of the groove 56 may thereafter be released to return to close into the original spacing D3 and thereby capture the tube 42 inside the groove. The longitudinal locking ribs 52, 54 may thus be captured/locked into the longitudinal grooves 60, 62. The locking ribs 52, 54 resultingly operate to lock the tube 42 inside the groove 56 and prevent ejection of the tube from the groove 56 during tire operation/rotation.

Alternatively, the tube 42 may be press inserted into the groove 56. The tube 42, being of uniform width dimensions and geometry, may be manufactured in large quantities. Moreover, a uniform dimensioned pump tube 42 may reduce overall assembly time, material cost, and non-uniformity of tube inventory. From a reliability perspective, this results in less chance for scrap.

The circumferential ridges D0 through D6 projecting into the groove 56 may increase in frequency (number of ridges per axial groove unit of length) toward the inlet passage of the tube 42, represented by the outlet device 70. Each of the ridges D0 through D6 may have a common radius dimension R4 within a range of 0.15 mm to 0.30 mm. The spacing between ridges D0 and D1 may be largest, the spacing between D1 and D2 the next largest, and so on until the spacing between ridges D5 and D6 is nominally eliminated. While seven ridges are shown, more or fewer ridges may be deployed at various frequency along the groove 56.

The projection of the ridges into the groove 56 by radius R4 may serve a twofold purpose. First, the ridges D0 through D6 may engage the tube 42 and prevent the tube from migrating, or “walking”, along the groove 56 during tire operation/rotation from the intended location of the tube. Secondly, the ridges D0 through D6 may compress the segment of the tube 42 opposite each ridge to a greater extent as the tire 12 rotates through its rotary pumping cycle, as explained above. The flexing of the sidewall may manifest a compression force through each ridge D0 through D6 and may constrict the tube segment opposite such ridge to a greater extent than otherwise would occur in tube segments opposite non-ridged portions of the groove 56. As seen in FIGS. 10A and 10B, as the frequency of the ridges increases in the direction of air flow, a pinching of the tube passageway 43 may progressively occur until the passageway constricts to the size shown at numeral 136, gradually reducing the air volume and increasing the pressure. As a result, with the presence of the ridges, the groove 56 may provide variable pumping pressure within the tube 42 configured to have a uniform dimension therealong. As such, the sidewall groove 56 may be a variable pressure pump groove functioning to apply a variable pressure to a tube 42 situated within the groove. It will be appreciated that the degree of pumping pressure variation may be determined by the pitch or ridge frequency within the groove 56 and the amplitude of the ridges deployed relative to the diametric dimensions of the tube passageway 43. The greater the ridge amplitude relative to the diameter, the more air volume may be reduced in the tube segment opposite the ridge and pressure increased, and vice versa. FIG. 9 depicts the attachment of the tube 42 to the outlet device 70 and the direction of air flow on both sides into outlet device.

FIG. 11 shows a second alternative rib profile area located on both sides of the outlet to the outlet device 70. FIG. 12A shows an enlarged detail of the groove 56 with the alternative second rib profile and FIG. 12B shows an enlarged detail of the tube 42 pressed into the second rib profile. With reference to FIGS. 11, 12A, 12B, the ridges, or ribs, D0 through D6 in this alternative may have a frequency pattern similar to that described above in reference to FIGS. 10A, 10B, but with each rib having a unique respective amplitude as well. Each of the ribs D0 through D6 may generally have a semi-circular cross-section with a respective radius of curvature R1 through R7, respectively. The radii of curvatures of the ridges/D0 through D6 may be within the exemplary range: Δ=0.020 mm to 0.036 mm.

The number of ridges D0 through D6 and respective radii of each ridge may be constructed outside the above ranges to suit other dimensions or applications. The increasing radius of curvature in the direction of air flow may result in the ridges D0 through D6 projecting at an increasing amplitude and, to an increasing extent, into the passageway 43 toward the outlet device 70. As such, the passageway 43 may constrict to a narrower region 138 toward the outlet device 70 and cause a correspondingly greater increase in air pressure from a reduction in air volume. The benefit of such a configuration is that the tube 42 may be constructed smaller than otherwise necessary in order to achieve a desired air flow pressure along the passageway 43 and into the tire cavity 40 from the outlet device 70. A smaller sized tube 42 may be economically and functionally desirable in allowing a smaller groove 56 within the tire 12 to be used, thereby resulting a minimal structural discontinuity in the tire sidewall.

FIGS. 13A through 13C show another tube 42 and groove 56 detail in which the detent ribs 90 of FIG. 8A through 8C are eliminated as a result of rib and groove modification. This tube 42 may have an external geometry and passageway configuration with indicated dimensions within ranges specified as follows:

D1=2.2 to 3.8 mm;

D2=0.5 to 0.9 mm;

D3=0.8 to 1.0 mm;

R4=0.15 to 0.30 mm;

L1=3.65 to 3.8 mm;

L2=2.2 to 2.3 mm;

L3=1.8 to 2.0 mm.

The above ranges may be modified to suit a particular dimensional preference, tire geometry, or tire application. The external configuration of the tube 42 may include beveled surfaces 138, 140 adjoining the end surface 48; parallel and opposite straight intermediate surfaces 142, 144 adjoining the beveled surfaces, respectively; and a radiused nose, or forward surface 146, adjoining the intermediate surfaces 142, 144. As seen from FIGS. 13B and 13C, the tube 42 may be compressed for press insertion into the groove 56 and, upon full insertion, expand. The constricted opening of the groove 56 at the sidewall surface may retain the tube 42 securely within the groove 56.

FIGS. 14A through 14C show another tube 42 and groove 56 configuration. FIG. 14A is an enlarged view and 14B is a detailed view showing the tube 42 compressed and inserted into the groove 56. FIG. 14C is a detailed view showing the tube 42 fully inserted into the groove 56. The tube 42 may be generally elliptical in cross-section inserting into a like-configured groove 56. The groove 56 may have a narrow entryway formed between opposite parallel surfaces 148, 150. In FIGS. 14A through 14C, the tube 42 is configured having an external geometry and passageway configuration with dimensions within the ranges specified as follows:

D1=2.2 to 3.8 mm;

D2=0.5 to 0.9 mm;

D3=0.8 to 1.0 mm;

R4=0.15 to 0.30 mm;

L1=3.65 to 3.8 mm;

L2=2.2 to 2.3 mm;

L3=1.8 to 2.0 mm

The above ranges may be modified to suit a particular dimensional preference, tire geometry, or tire application. FIGS. 15A through 15C show another tube 42 and groove 56 configuration. FIG. 15A is an enlarged view and FIG. 15B is a detailed view showing the tube 42 compressed and inserted into the groove 56. FIG. 15C is a detailed view showing the tube 42 fully inserted into the groove 56. The tube 42 may be generally have a parabolic cross-section for inserting into a like-configured groove 56. The groove 56 may have an entryway sized to closely accept the tube 42 therein. The ridges 66 may engage the tube 42 once inserted into the groove 56. In FIGS. 15A through 15C, the tube 42 has an external geometry and passageway configuration with dimensions within the ranges specified as follows:

D1=2.2 to 3.8 mm;

D2=0.5 to 0.9 mm;

D3=2.5 to 4.1 mm;

L1=3.65 to 3.8 mm;

L2=2.2 to 2.3 mm;

L3=1.8 to 2.0 mm

The above ranges may be modified to suit a particular dimensional preference, tire geometry, or tire application if desired.

From the forgoing, it will be appreciated that the present invention may comprise a bi-directionally peristaltic pump assembly 14 for air maintenance of a tire 12. The circular air tube 42 may flatten, segment by segment, and close in the tire footprint 100. The air inlet device 68 may include an outer filter sleeve 92 formed of porous cellular material and thereby render the air inlet device 68 self-cleaning. The outlet device 70 may employ a valve unit (see co-pending U.S. patent application Ser. No. 12/775,552, filed May 7, 2010, incorporated herein by reference). The peristaltic pump assembly 14 may pump air through rotation of the tire 12 in either direction, one half of a revolution pumping air to the tire cavity 40 and the other half of a revolution pumping air back out of the inlet device 68. The peristaltic pump assembly 14 may be used with a secondary tire pressure monitoring system (TPMS) (not shown) that may serve as a system fault detector. The TPMS may be used to detect any fault in the self-inflation system of the tire assembly 10 and alert the user of such a condition.

The tire air maintenance system 10 may further incorporate a variable pressure pump groove 56 with one or more inwardly directed ridges or ribs 66 engaging and compressing a segment of the air tube 42 opposite such rib(s). The pitch or frequency of the ribs may increase toward the outlet device 70 for gradually reducing air volume within the passageway 43 by compressing the tube 42. The reduction in air volume may increase air pressure within the passageway 43 and thereby facilitate a more efficient air flow from the tube 42 into the tire cavity 40. The increase in tube pressure may be achieved by engagement by the ribs 66 of the groove 56 and the tube 42 having uniform dimensions along the tube length. The tube 42 may thus be made of uniform dimension and of relatively smaller size without compromising the flow pressure of air to the tire cavity 40 for maintaining air pressure. The pitch and amplitude of the ridges 66 may both be varied to better achieve the desired pressure increase within the passageway 43.

Structures in a pneumatic tire may require the embedding of certain rigid parts, functional devices, and/or connectors into adhering onto the rubber of the tire. For example, the structures 14, 42, 68, 70, 101, 202, etc. of the example air maintenance tire 10 described above may require embedding/adherence. Such structures 14, 42, 68, 70, 101, 202, etc. typically encounter high stresses during operating conditions of the tire 10. Thus, strong bonding of such structures 14, 42, 68, 70, 101, 202, etc. is desired since a bond break at the structure's 14, 42, 68, 70, 101, 202, etc. surface will likely lead to destruction of the assembly 14 and/or the integrity of the tire 10 as a whole.

For example, a polyamide elbow-like structure 70 may be bonded to a tire 10 in order to define a built-in tube-like cavity (FIG. 3C). This structure 70 may thereby allow rerouting of pressurized air to a pump assembly 14 and from there, into a tire cavity 40, as well as to make a connection to the outside for providing fresh unpressurized air to the pump assembly.

The establishment of the self inflating tire technology (SIT/AMT) described above may require a filter 200 in accordance with the present invention as part of such a pneumatic tire 12 for filtering air prior to its entry into the tire cavity 40. The filter 200 may require sufficiently high air permeation, as well as acceptable cost, chemical and mechanical durability, ability to detain water, and/or complexity. The filter 200 may thus be constructed of a porous plastic.

Conventionally, porous plastics (e.g., polypropylene, polyethylene, teflon, etc.) are offered as air filter material for several applications. These porous plastics combine flexibility in shape, chemical durability, potential to detain water, low complexity, and low manufacturing cost to demonstrate a novel and extremely useful filter material for SIT/AMT tires, such as the pneumatic tire 12. The properties of air permeation, chemical durability, and water separation potential may be reduced to a mere material property relating to pore size distribution and type of polymer. As an example, screws may be manufactured of porous plastics thereby not requiring embedding the material into a metal or plastic frame material (e.g., threads mechanically secure filter 200 to the pneumatic tire 12). This may reduce complexity to a lowest level possible and accordingly minimize manufacturing cost of the filter 200 and/or filter assembly.

As shown in FIG. 1, a grub screw 200 of a porous plastic material may be threaded into a connector 202 that is embedded in the sidewall 30, 32 of a pneumatic self inflating tire 12 thereby filtering an air flow between the atmosphere, through the filter 200, into the tire cavity 40. Such a filter 200 may also hold up well as part of a pneumatic tire 12 rotating and under load. Further, such a filter 200 comprises an improvement over conventional woven metal filters in corrosion is eliminated, ability to detain water is enhanced, and cost and complexity are reduced.

As shown in FIGS. 17A, 17B, 18A,18B, an air filter 1700 in accordance with the present invention may be used in an AMT, as described above. The air filter 1700 may allow water droplets to run over a membrane external surface 1711, and thus clean it, without blocking an inlet to the AMT system. The air filter 1700 may include a filter support housing 1720 defining a membrane seat 1721 for receiving an air membrane 1710 used for air filtration. The filter support housing 1720 may also include an air outlet 1723 for supplying air to the pump system described above. Alternatively, multiple membranes 1710 may be stacked in order to utilize differing porosities of different membrane materials. To produce a self-cleaning effect, a membrane external surface 1711 may be constructed of a hydrophobic material for avoiding all liquid adhesion to it. The liquid flow on the membrane surface 1711 may remove particles deposited on the membrane surface, thereby cleaning it. The hydrophobic material may be polytetrafluoroethylene (PTFE), which may be integrated into the external surface 1711 of the membrane 1710 or used to coat or spray the external surface of the membrane. A filter lock member 1730 may clamp the membrane 1710 and keep it secured to the filter support housing 1720. The filter lock member 1730 may include barbs, threads, and/or clips. The filter lock member 1730 may include air inlets 1733 for supplying the pump system described above. The external surface 1731 of the lock member 1730 may be treated with a hydrophilic material to capture water and/or other liquid for cleaning the membrane surface 1711. Conversely, channels 1733 leading toward the membrane 1710 may be coated or sprayed with the hydrophobic material to facilitate liquid flow through the air filter 1700. The air filter 1700 may further include an O-ring 1740 for sealing the filter support housing 1720 to the tire 12.

Variations in the present invention are possible in light of the description of it provided herein. While certain representative examples and details have been shown for the purpose of illustrating the present invention, it will be apparent to those skilled in this art that various changes and modifications may be made therein without departing from the scope of the present invention. It is, therefore, to be understood that changes may be made in the particular examples described which will be within the full intended scope of the present invention as defined by the following appended claims. 

What is claimed:
 1. A method for maintaining air pressure in a pneumatic tire cavity, the method comprising the steps of: placing a filter between the pneumatic cavity and atmosphere, the filter being constructed of a hydrophobic material for avoiding liquid adhesion; deforming an air passageway segment by segment between an expanded condition and an at least partially collapsed condition in response to respective segment by segment deformation of a sidewall groove when radially within a rolling tire footprint; coating an air inlet of the filter with the hydrophobic material to facilitate liquid flow through the filter; and capturing liquid by a hydrophilic material.
 2. The method as set forth in claim 1 further including the step of securing an air membrane to a membrane seat of a filter support housing.
 3. The method as set forth in claim 2 further including the step of supplying air to the air passageway.
 4. The method as set forth in claim 3 wherein the air membrane comprises polytetrafluoroethylene.
 5. The method as set forth in claim 1 further including the step of stacking a membrane in order to utilize differing porosities of different membrane materials for air filtration.
 6. The method as set forth in claim 2 further including the step of sealing the filter support housing to the tire with an O-ring.
 7. The method as set forth in claim 6 further including the step of securing the air membrane to the filter support housing by a filter lock member.
 8. The method as set forth in claim 7 further including the step of supplying ambient air to the air passageway by the air inlet of the filter. 